Simultaneous productions of high-purity calcium carbonate and amorphous nanosized silica-rich gel from waste concrete powder by alkaline treatment and carbonation

IF 8 2区环境科学与生态学 Q1 ENVIRONMENTAL SCIENCES

Journal of Environmental Management Pub Date : 2024-11-16 DOI:10.1016/j.jenvman.2024.123319

Lei Liu , Guangfeng Ou , Lei Xu , Naoki Ogiwara , Sayaka Uchida , Huaming Yang , Yuya Sakai

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Abstract

Simultaneous productions of high-purity CaCO₃ (calcium carbonate) and amorphous nanosized SiO₂-rich (silica-rich) gel from waste concrete powder remain quite challenging, and thus the high-value added utilization of waste concrete powder is significantly limited. A novel technology involving a combination of alkaline treatment and carbonation, has been proposed for the greatly enhanced utilization of waste concrete powder. Through alkaline treatment, CaCO₃ and SiO₂-rich gel formed during carbonation of concrete powder were transformed into Ca(OH)₂ (calcium hydroxide) and Na₂SiO₃ (sodium metasilicate), respectively. Subsequently, Ca(OH)₂ and Na₂SiO₃ were separated. As a result, CaCO₃ with a high purity of 98.54% and amorphous nanosized SiO₂-rich gel were obtained via carbonation, and the recovery ratio of CaCO₃ was 81.46%. Furthermore, the concrete powder exhibited a high CO₂ (carbon dioxide) uptake efficiency of 0.24g CO₂/g. 30.31 Mt CaCO₃ and 2.77 Mt SiO₂-rich gel productions as well as 38.54 Mt CO₂ emission reduction could be realized via recycling a quarter of annually generated waste concrete powder worldwide.

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利用碱处理和碳化法同时从废弃混凝土粉末中制备高纯度碳酸钙和无定形纳米富硅凝胶。

从废弃混凝土粉末中同时制备高纯度 CaCO3（碳酸钙）和无定形纳米级富含 SiO2（二氧化硅）凝胶仍具有相当大的挑战性，因此废弃混凝土粉末的高附加值利用受到很大限制。为了大大提高废弃混凝土粉的利用率，有人提出了一种将碱处理和碳化相结合的新技术。通过碱处理，混凝土粉碳化过程中形成的 CaCO3 和富含 SiO2 的凝胶分别转化为 Ca(OH)2（氢氧化钙）和 Na2SiO3（偏硅酸钠）。随后，Ca（OH）2 和 Na2SiO3 分离出来。结果，通过碳化获得了纯度高达 98.54% 的 CaCO3 和富含 SiO2 的无定形纳米凝胶，CaCO3 的回收率为 81.46%。此外，混凝土粉末的 CO2（二氧化碳）吸收效率高达 0.24 克 CO2/克。通过回收利用全球每年产生的四分之一的废弃混凝土粉末，可生产 3 031 万吨 CaCO3 和 277 万吨富含 SiO2 的凝胶，并减少 3 854 万吨二氧化碳排放量。

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来源期刊

Journal of Environmental Management 环境科学-环境科学

CiteScore

13.70

自引率

5.70%

发文量

2477

审稿时长

84 days

期刊介绍： The Journal of Environmental Management is a journal for the publication of peer reviewed, original research for all aspects of management and the managed use of the environment, both natural and man-made.Critical review articles are also welcome; submission of these is strongly encouraged.